Electric valve converting system



April 19, 1938. R. LOMBARDI ELECTRIC VALVE CONVERTING SYSTEM PHASE TO IGRIDS PHASE T0 CA THODE Filed June 26, 1934 TO GI? A MD CATHOHEInventor: Renato Lombardi H is Attorngg- Patented Apr. 19, 1938 UNITEDSTATES PATENT OFFICE Renato Lombardi, Milan, Italy, assignor to GeneralElectric Company, a corporation of New York Application June 26, 1934,Serial No. 732,448 In Italy August 9, 1933 13 Claims.

My invention relates to electric valve converting systems, and moreparticularly to such systems including electric valves for transmittingenergy between direct and alternating current circuits.

Heretofore, there have been devised numerous apparatus includingelectric valves for transmitting energy between direct and alternatingcurrent circuits, wherein rectifiers or inverters have been used topermit energy flow in one direction between the two systems.Furthermore, it is well known in the art that the direction of energyflow between the two systems may be reversed by reversing the connectionof the electric valve apparatus on the direct current side. Generally,however, this has necessitated the interruption of the connectionbetween the two systems for the purpose of reversal of the operationofthe valve apparatus and this necessarily interrupts the continuitybetween the two systems. Such arrangements have been proposed for use ondirect current traction systems or locomotives in which it was desiredto apply the well known scheme of regenerative braking. In someinstances these locomotives have been equipped with direct currentmotors and the alternating current received from the trolley wasrectified by the apparatus carried by the locomotive. In other systems,however, alternating current feeder systems have supplied convertingapparatus which fed the direct current trolley system. It will beapparent that where regenerative braking is used in such tractionsystems there will be a reversal of the flow of energy between the twocurrent systems. Obviously, of course one of the chief disadvantages ofthe prior arrangements has been that there has been a discontinuitybetween the two current systems whenever the electric valve apparatuswas reversed in operation, and that often reversal of such apparatusoccurred at the improper time.

It is an object of my invention, therefore, to provide an improvedelectric valve converting system for transmitting energy between directand alternating current circuits which will overcome the above mentioneddisadvantages of the arrangements of the prior art, and which will besimple and reliable in operation.

It is another object of my invention to provide an improved electricvalve system which will obtain an accurate and reliable indication ofthe conditions under which it is desired that the operation of theelectric valve converter is to be reversed, and to avoid needlessreversal of the electric valve converter connections.

It is a further object of my invention to provide an electric valveconverting system wherein the connections of the inverting apparatus maybe reversed Without interrupting the electrical continuity between thealternating current and the direct current systems.

In accordance with my invention, the direct and alternating currentcircuits are interconnected through a pair of electric valve convertingapparatus which may be of any of the several types well known in theart, although I prefer to use apparatus of the grid controlled electricvalve type. One of these electric valve converting apparatus isconnected between the two current systems so as to operate in adirection in which the predominant energy flow occurs, while the otherelectric valve apparatus, which may be of small capacity, is arranged tobe connected in a manner so as to operate in a direction opposite to thefirst electric valve apparatus and to be connected between the twosystems during the time that the reversal of the connections to thefirst apparatus occur. Thus, at all times, there is a continuity betweenthe two current systems. Furthermore, in accordance with my invention,there is provided a device for detecting the conditions under which theautomatic conversion of the direction of power transmission between thetwo networks becomes necessary. This detection device prepares thecircuit and does the actual reversal of the connection to the mainelectric valve converter.

For a better understanding of my invention, together with other andfurther objects thereof, reference may be had to the followingdescription taken in connection with the accompanying drawing, in whichFig, 1 illustrates an embodiment of my invention for transmitting energybe tween a three-phase alternating current circuit and a direct currentcircuit, and Fig. 2 schematically shows the grid circuit excitationarrangement.

Referring to Fig. 1 of the drawing, there is illustrated a polyphasevalve converting system for transmitting energy between the three-phasealternating current system H! and a direct current system H. A converterI2 of sufilcient capacity to carry any load which may appear across thedirect current lines H is connected between the direct current circuitand the alternating current circuit H) by means of the direct currentconductors H and the polyphase inductive networks l3 and 14.

While I have shown a multi-anode single-cathode vapor electric dischargedevice of the grid controlled type, it will be apparent to those skilledin the art that other electric discharge devices may be utilized or thata plurality of electric valves each having an anode, a cathode and agrid element, may be used in place of the multianode single-cathodedischarge device l2. An auxiliary electric discharge device l5 normallydisconnected, is arranged between the direct current line i I and thealternating current circuit iii through the medium of the polyphasenetworks I S and M. This electric discharge device i5 is arranged so asto operate as an inverter when connected to the direct current line ll.The grid control circuits for the electric valve discharge devices l2and have not been shown in detail, inasmuch as the particular form ortype of grid circuit forms no part of my invention and any suitable gridcontrol circuits may be used, as is well understood by those skilled inthe art.

In order to detect a condition precedent to a reversal of the normaldirection of the flow of energy between the alternating current circuitit and the direct current circuit H, an electroresponsive device is isarranged so as to have its energizing coil connected across a currentshunt I9 in circuit ii. As will be evident, the no load conditionsappearing across the connections ll will be an indication that there maybe a possibility of a reversal of the direction of energy flow betweenthe direct and alternating current circuits. The elcctroresponsivedevice, or relay i3, is normally energized so as to be in the positionshown when there is a flow of energy from the alternating currentcircuit to the direct current circuit. A low voltage circuit 2t,preferably alternating current in nature, supplies energy to theapparatus Which will be actuated in response to a cessation of areversal of the energy flow between the alternating and direct currentcircuits. Whenever the load across the rectifier i2 drops to zero therelay 18 becomes deenergized so that the armature drops to close itscontacts 2! thereby closing a circuit which energizes a relay 22. Therelay 22 when energized, closes a contact 23 which completes the circuitconnection of the inverter 55 with the direct current circuit II. Theinverter i5 has a capacity which is of the order of but a few per centof the normal capacity of the rectifier I2 and the grid excitation ofthe inverter it will be such that the voltage appearing across thedirect current circuit Ii, which, it will be remembered, is at a no loadcondition, can impress but a small current, as for example, .07 of 1% ofthe full load current of the rectifier l2, upon the alternating currentcircuit II]. If now, however, a reversal of the energy flow between thealternating and direct current circuits occurs, such as would be thecase when a regenerative locomotive is across the direct current line H,the voltage of he direct current circuit will increase so that thecurrent inverted by the inverter 55 will also increase. A maximum demandrelay 24 connected between the inverter I5 and one side of the directcurrent circuit M, will be energized as soon as the current load of theinverter has reached a certain value, as for example, .5 of 1% of thefull load current of the rectifier i2. I'he energization of the relay 24closes its contacts 25 thereby completing a circuit which energizes anactuating coil 25, for operating a reversing switch 2'! to one of itsoperating positions. This reversing switch is interposed between thedirect current circuit and the direct current leads H which areconnected to the electric discharge device !2. Thus, when the switch 2!has been actuated, the connections to the electric valve apparatus l2have been reversed so that this apparatus may now operate as aninverter. It will be noted, however, that the actuation of the armatureof the actuating coil 26 has caused its circuit to be interrupted bymeans of contacts 28, and that other contacts 29 and 33 aresimultaneously closed. The contacts 29 control the energization of aholding coil 30 which maintains switch 2? in the new position. Thecircuits controlled by contacts 33 to 4| will be described hereinafter.Inasmuch as a regenerative locomotive or a reversal of the direction ofnormal energy flow between the alternating and direct current circuitshas caused the actuation of the switch 2'7, it will be apparent thatcurrent is now flowing through the electric discharge device l2, whichis operating as an inverter, and through the shunt l9. A current flowthrough the electric discharge device l2 which is now operating as aninverter, also produces a flow of current through the actuating coil ofthe relay I 8. As a result of this, the armature of the relay I8 isdrawn into its illustrated position and its contacts 2! which controlthe energization of the actuating coil of the relay 22 have beenseparated, so that the armature of this relay now drops to open itscontacts 23. This opening of the contacts 23 disconnects the inverter 15from the line and also permits the relay 24 to return to its deenergizedposition.

If at a subsequent time this regenerative condition ceases so that thedirect current circuit H is at a no load condition, current will nolonger be flowing through the shunt I9 and through the actuating coil ofthe relay l8, with the result that the armature of this relay will nowdrop, thereby closing the contacts 3| which are connected in seriesrelation with the previously mentioned closed contacts 33 of relay 26 tocontrol the energization of the coil of a second relay 32 for operatingswitch 2?. Relay 32 is of the time delay type which will operate onlyafter a predetermined time interval. When this time interval has beencompleted, the relay 32 will 0perate to restore the switch 21 to itsoriginal position. In doing so, however, the contacts 33 which are inseries with the circuit of the energizing coil of the relay 32 areopened thereby interrupting the operating circuit of relay 32. sametime, however, a set of contacts 34 operated by relay 32 are closed.These contacts are in the circuit of a holding coil 35, which maintainsthe switch 2'! in its restored position. The

time delay relay 32 operates to prevent needless e reversal of theswitch 2'! in case the regenerative condition of the lines It ismomentarily interrupted.

t will be apparent from the description of the apparatus that at thetime when the regenerative condition has ceased to exist so that therelay It has become deenergized thereby closing contacts 3|, it has alsoclosed contacts 2|, which in turn again connects the inverter 15 acrossthe line H by means of the circuit previously described, so that duringthe time interval necessary for the coil of the relay 32 to complete itsoperation the inverter 15 is connected across the direct current line.Hence,- during the time of restoration of the switch 2? to its originalposition the continuity of interconnection of the apparatus between thedirect and alternating current lines has been maintained.

In Fig. 2 there is disclosed diagrammatically the grid circuitarrangement which is controlled At the by the switch contacts 36 to 4|as the main switch mechanism is operated in Fig. 1. The righthandcontacts of each of the pairs of contacts 36 to 4| are connected to thealternating current line I. The left-hand contacts of the pairs ofcontacts 36, 38 and 40 are connected to a phase shifter indicated by therectangle 42. The lefthand contacts of the pairs of contacts 31, 39 and4| are connected to a phase shifter indicated by the rectangle 43. Thephase shifters 42 and 43 are connected to the primary windings of thegroup of grid circuit transformers indicated by the rectangle 44. Thesecondary windings of the grid circuit transformers indicated by therectangle 44 are connected respectively to the cathode and the grids ofthe rectifier device I 2.

In Fig. 1 a phase shifter is denoted by the rectangle 45 and this isconnected to energize the primary windings of the group of grid circuittransformers indicated by the rectangle 46. The

Y secondary windings of the grid circuit transformers indicated by therectangle 46 are connected, respectively, to the cathode and to thegrids of the rectifier device l5. As will be apparent to those skilledin the art, the phase shifters denoted by the rectangles 42, 43 and 45may be any of the phase shifting circuits or devices well known in theart and the grid circuit transformers utilized in the rectangles 44 and46 may be of the type which produce peaked wave form so as to supply asharp impulse of short duration. Obviously, of course, the grid circuitmay include a source of biasing voltage and the customary currentlimiting resistors.

While in the above arrangement, inverter has been connected so as to benormally disconnected from the direct current line during the time thatthe electric discharge device [2 is con nected to the direct currentcircuit, it will be apparent to one skilled in the art, however, thatcomplete continuity of interconnection between the direct andalternating current circuits may also be obtained by connecting theinverter |5 so that it will be connected continuously across the directcurrent circuit. This will be accomplished by omitting the followingelements which include the contacts 2| of the relay l8, the relay 22 andits contacts 23. The relay 24, however, will operate in its usual mannerso that at no load conditions the relay 24 will remain deenergized, butwhenever a regenerative condition occurs across the line this relay willpick up so as to energize the coil of the actuating relay 26 whichcontrols the actuation of the reversing switch 21.

While I have shown and described my invention in connection with certainspecific embodiments, it will, of course, be understood that I do notwish to be limited thereto, since it is apparent that the principlesherein disclosed are susceptible of numerous other applications, andmodifications may be made in the circuit arrangement and in theinstrumentalities employed without departing from the spirit and scopeof my invention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. The combination in an electric energy converting system of a directcurrent circuit, an alternating current circuit, a converterinterconnecting said circuits for transmitting energy normally in onedirection between said circuits, an auxiliary converter for transmittingenergy between said circuits in a direction opposite to that of saidfirst converter, means cooperating with said auxiliary converter fordetecting a condition prececonnecting said circuits for transmittingenergynormally in one direction between said circuits, an auxiliaryelectric valve converter for transmitting energy between said circuitsin a direction opposite to that of said first converter, meanscooperating with said auxiliary converter for detecting a reversal ofthe direction of the normal energy fiow between said circuits, and meansactuated by said first means for reversing the direction of operation ofsaid first converter.

3. An electric energy converting system comprising a direct currentcircuit, an alternating current circuit, a converter interconnectingsaid circuits for transmitting energy normally in one direction betweensaid circuits, an auxiliary converter arranged for transmitting energybetween said circuits in the opposite direction, said auxiliaryconverter being normally disconnected from one of said circuits, meansresponsive to a cessation of energy flow between said circuits forconnecting said auxiliary converter to said circuits, and meanscooperating with said auxiliary converter for detecting the reversal ofthe direction of normal energy flow between said circuits and forreversing the direction of operation of said first converter.

4. The combination in an electric energy converting system of a directcurrent circuit, an alternating current circuit, a converterinterconnecting said circuit for transmitting energy normally in onedirection between said circuits, means for detecting a conditionprecedent to a reversal of the direction of the normal energy flowbetween said circuits, means including an auxiliary converter actuatedby said first means for reversing the direction of operation of saidfirst converter and for maintaining a continuity of interconnectionbetween said circuits, and means for restoring the first converter tothe original operating conditions in response to a cessation of energyflow between said circuits.

5. An electric energy converting system comprising a direct currentcircuit, an alternating current circuit, an electric valve converterinterconnecting said circuits for transmitting energy normally in onedirection between said circuits, an auxiliary electric valve converterfor transmitting energy between said circuits in the opposite direction,means cooperating with said auxiliary converter for detecting a reversalof the direction of the normal energy flow between said circuits, meansactuated by said first means for reversing the direction of operation ofsaid first converter, and means for restoring said first converter tothe original operating conditions in response to a cessation of energyflow between said circuits.

6. An electric valve converting system comprising a direct currentcircuit, an alternating current circuit, a converter having connectionswith said circuits for transmission of energy normally in one directionbetween said circuits, an auxiliary converter arranged for connection tosaid circuits for transmission of energy in an opposite direction, meansresponsive to a cessation of energy fiow between said circuits forconnecting said auxiliary converter to said circuits, means responsiveto energy flow in an opposite direction between said circuits forreversing said .connec tions of said first converter, and meansresponsive to a subsequent cessation of energy fiow between saidcircuits for restoring said converting system to the original condition.

'7. An electric energy converting system 00.1 prising an alternatingcurrent circuit, a direct current circuit, a converter havingconnections with said circuits for transmission of energy normally inone direction between said circuits, a small auxiliary converterarranged for interconnecting said circuits for transmission of energy inthe opposite direction, means responsive to a cessation of a flow ofenergy through said first converter for connecting said auxiliaryconverter to said circuits, means responsive to a predetermined energyflow through said auxiliary converter for reversing said connections ofsaid first converter for transmitting energy in the opposite direction,and means responsive to subsequent cessation of energy flow through saidfirst converter for restoring said connections to the originalcondition.

8. An electric energy converting system comprising an alternatingcurrent circuit, a direct current circuit, an electric valve converterinterconnecting said circuits, an auxiliary electric valve converter fortransmitting energy between said circuits in a direction opposite to thenormal direction of energy fiow through said first electric valveconverter, means responsive to a predetermined energy flow through saidauxiliary converter for reversing the direction of en ergy flow throughsaid first electric valve converter, and means responsive to a cessationof energy flow through said first electric valve converter for restoringsaid first valve converter to said original operating condition.

9. An electric energy converting system comprising an alternatingcurrent circuit, a direct current circuit, an electric valve converterinterconnecting said circuits, an auxiliary converter for transmittingenergy between said circuits in a direction opposite to the normaldirection of energy flow through said electric valve converter, meansresponsive to a predetermined energy flow through said auxiliaryconverter for reversing the direction of energy flow through saidelectric valve converter, and means responsive to a cessa tion of energyflow through said electric valve converter for restoring said valveconverter to said original operating condition after a predeterminedtime interval.

10. An electric energy converting system comprising an alternatingcurrent circuit, a direct current circuit, an electric valve converterinterconnecting said circuits, an auxiliary converter normallydisconnected and arranged for transmitting energy between said circuitsin a direction opposite to the normal direction or energy flow throughsaid electric valve converter, means responsive to a predeterminedminimum energy flow through said valve converter for connecting saidauxiliary converter to said circuits, and means responsive to apredetermined energy flow through said auxiliary converter for reversingthe direction of energy flow through said electric valve converter.

11. An electric energy converting system comprising an alternatingcurrent circuit, a direct current circuit, an electric valve converterinterconnecting said circuits, an auxiliary converter normallydisconnected and arranged for transmitting energy between said circuitsin a direction opposite to the normal energy flow through said electricvalve converter, means responsive to a predetermined minimum energy flowthrough said Valve converter for connecting said auxiliary converter tosaid circuits, means responsive to a predetermined energy flow throughsaid auxiliary converter for reversing the direction of energy flowthrough said electric valve converter, and means responsive to acessation of energy flow through said valve converter for restoring saidvalve converter to the original condition after a predetermined timeinterval.

12. An electric energy converting system comprising an alternatingcurrent circuit, a direct current circuit, an electric valve convertingapparatus interconnecting said circuits normally transmitting energyfrom said alternating current circuit to said direct current circuit, anauxiliary converting apparatus interconnecting said circuits fortransmitting energy from said direct current circuit to said alternatingcurrent circuit, means connected between said auxiliary convertingapparatus and said direct current circuit for reversing the operation ofsaid valve converting apparatus in response to a predetermined energyfiow through said auxiliary converting apparatus, and means responsiveto a cessation of energy flow through said electric valve convertingapparatus for restoring said valve converting apparatus to said normaloperating condition after a predetermined time interval.

13. A reversible electrical conversion system for transmitting power ineither direction without interruption at time of reversal, comprisingtwo electric current lines, one of which is a directcurrent linecomprising at least two independent parallel connected converters, meansassociated with each of said converters for determining the operativecondition thereof and relay means responsive to the electrical operatingvalues of the direct-current line for controlling said means in sequencewith said operating values so that upon reversal of current flow betweensaid lines one of said converters is connected for reverse operationbefore the reversal of power flow.

RENATO LOMBARDI.

